THIEPVAL, FRANCE - JUNE 30: Catherine, Duchess of Cambridge and Prince William, Duke of Cambridge attend part of a military-led vigil to commemorate the 100th anniversary of the beginning of the Battle of the Somme at the Thiepval memorial to the Missing in June 30, 2016 in Thiepval, France. The event is part of the Commemoration of the Centenary of the Battle of the Somme at the Commonwealth War Graves Commission Thiepval Memorial in Thiepval, France, where 70,000 British and Commonwealth soldiers with no known grave are commemorated. (Photo by Tim Rooke - Pool/Getty Images)